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FASEB Journal : Official Publication of... Jul 1994Fundamental, yet unresolved, issues in developmental neurobiology concern the relative influence of genetic vs. epigenetic factors in determining cell phenotype and... (Review)
Review
Fundamental, yet unresolved, issues in developmental neurobiology concern the relative influence of genetic vs. epigenetic factors in determining cell phenotype and establishing positional relationships among clonally related cells in the developing and mature vertebrate central nervous system (CNS). Advances in our understanding of how cells acquire their identity awaited a means to introduce lineage tracers into dividing cells of the developing CNS where the progenitor cells, which are situated in a neuroepithelial layer adjacent to the ventricles, generally are small and inaccessible. The technique of retroviral-mediated gene transfer, whereby a heritable, easily detectable marker such as the gene for lacZ is integrated into the DNA of individual progenitor cells, has been used to analyze the lineage relationships of cells in the CNS and to derive the types of progenitor cells in the proliferative zones at different developmental stages. Collectively, these studies indicate that the CNS uses more than one strategy to achieve cell diversity. The analysis of the phenotypic composition of the cells within a clone indicates that there are predominantly separate progenitor cells for each of the main cell types comprising the cerebral cortex by the onset of cortical neurogenesis, although in other systems mostly multipotential progenitor cells persist throughout neurogenesis. Here I will compare and contrast the inferred role of cell lineage in the developing cerebral cortex and olfactory bulb, where postmitotic neurons migrate relatively long distances from their site of generation to their final destination, with that in other regions of the CNS in which the displacement of postmitotic neurons from their birthplace is significantly less.
Topics: Animals; Central Nervous System; Phenotype; Prosencephalon; Retroviridae; Stem Cells; Vertebrates
PubMed: 8050671
DOI: 10.1096/fasebj.8.10.8050671 -
Cell and Tissue Research Apr 2001Intrasexual as well as intersexual dimorphisms were found in the prosencephalon and mesencephalon of adult Oncorhynchus nerka (red/sockeye salmon). These dimorphisms are... (Comparative Study)
Comparative Study
Intrasexual as well as intersexual dimorphisms were found in the prosencephalon and mesencephalon of adult Oncorhynchus nerka (red/sockeye salmon). These dimorphisms are concerned with the position of the preoptic nucleus, nucleus lateralis tuberis, habenula, third ventricle, tectal ventricles, preoptic recess, recessus lateralis, horizontal commissure, posterior commissure, and toral commissure. The intrasexual dimorphism was characterized by either a rostral ("r"-pattern) or a caudal ("c"-pattern) position of the preoptic region as well as varying locations of other structures within the prosencephalon. As compared to "c"-pattern fish, the preoptic nucleus and nucleus lateralis tuberis were located more rostral, and the habenula was positioned further caudal, in "r"-type animals. The intersexual dimorphism was also characterized by different positions of the structures listed above. With the exception of the preoptic nucleus, all of these were located further rostral in "r"-pattern females than in type "r" males. In "c"-pattern females, they were positioned further caudal than in type "c" males. The number of neurons in the parvocellular and in the magnocellular portion of the preoptic region differed in the two genders with respect to "r"- as well as "c"-pattern fish. Males had more neurons than females in both the magno- and the parvocellular subdivisions of the preoptic region. In "r"- and "c"-pattern fish, the average size of magnocellular preoptic neurons was larger in females than in males. The observed intersexual variations may reflect gender-specific differences in the control of the pituitary. Functional correlates of intrasexual dimorphism are obscure.
Topics: Animals; Cell Count; Diencephalon; Female; Habenula; Lateral Thalamic Nuclei; Male; Neurons; Preoptic Area; Prosencephalon; Salmon; Sex Characteristics; Telencephalon; Third Ventricle
PubMed: 11383879
DOI: 10.1007/s004410000335 -
Annals of the New York Academy of... Jun 1999Cortical acetylcholine (ACh) mediates the detection, selection, and processing of stimuli and associations, and the allocation of processing resources for these... (Review)
Review
Cortical acetylcholine (ACh) mediates the detection, selection, and processing of stimuli and associations, and the allocation of processing resources for these attentional functions. For example, loss of cortical cholinergic inputs impairs the performance of rats in tasks designed to assess sustained or divided attention. Intrabasalis infusions of benzodiazepine receptor (BZR) agonists block increases in cortical ACh efflux and impair attentional abilities. Studies on the regulation of cortical ACh efflux by nucleus accumbens (NAC) dopamine (DA) demonstrate that increases in cortical ACh efflux are attenuated by intra-accumbens administration of D1 and, more potently, D2 receptor antagonists. These and other data support the hypothesis that NAC DA, via GABAergic projections to the basal forebrain, controls the excitability of basal forebrain cholinergic neurons. As increases in NAC DA have been hypothesized to represent a major neuronal mediator of schizophrenia and the compulsive use of addictive drugs, the data predict that the abnormal regulation of cortical ACh release represents a crucial neuronal mechanism mediating the cognitive components of these psychopathological disorders.
Topics: Acetylcholine; Afferent Pathways; Animals; Attention; Cerebral Cortex; Humans; Mental Disorders; Nervous System Diseases; Prosencephalon; Rats
PubMed: 10415659
DOI: 10.1111/j.1749-6632.1999.tb09277.x -
Annual Review of Neuroscience 2002Mammalian reproduction depends on the coordinated expression of behavior with precisely timed physiological events that are fundamentally different in males and females.... (Review)
Review
Mammalian reproduction depends on the coordinated expression of behavior with precisely timed physiological events that are fundamentally different in males and females. An improved understanding of the neuroanatomical relationships between sexually dimorphic parts of the forebrain has contributed to a significant paradigm shift in how functional neural systems are approached experimentally. This review focuses on the organization of interconnected limbic-hypothalamic pathways that participate in the neural control of reproduction and summarizes what is known about the developmental neurobiology of these pathways. Sex steroid hormones such as estrogen and testosterone have much in common with neurotrophins and regulate cell death, neuronal migration, neurogenesis, and neurotransmitter plasticity. In addition, these hormones direct formation of sexually dimorphic circuits by influencing axonal guidance and synaptogenesis. The signaling events underlying the developmental activities of sex steroids involve interactions between nuclear hormone receptors and other transcriptional regulators, as well as interactions at multiple levels with neurotrophin and neurotransmitter signal transduction pathways.
Topics: Animals; Cell Differentiation; Genes, Regulator; Gonadal Steroid Hormones; Humans; Nerve Growth Factors; Neural Pathways; Neuronal Plasticity; Prosencephalon; Reproduction; Sex Characteristics; Signal Transduction
PubMed: 12052919
DOI: 10.1146/annurev.neuro.25.112701.142745 -
Behavioural Brain Research Nov 2000Studies over the last decade have shown that the basal forebrain (BF) consists of more than its cholinergic neurons. The BF also contains non-cholinergic neurons,... (Review)
Review
Studies over the last decade have shown that the basal forebrain (BF) consists of more than its cholinergic neurons. The BF also contains non-cholinergic neurons, including gamma-aminobutyric acid-ergic neurons which co-distribute and co-project with the cholinergic neurons. Both types of neuron project, in variable proportions, to the cerebral cortex, hippocampus, thalamus, amygdala, and olfactory bulb, whereas descending projections to the posterior hypothalamus and brainstem nuclei are predominantly non-cholinergic. Some of the cholinergic and non-cholinergic projection neurons contain neuropeptides such as galanin, nitric oxide synthase, and possibly glutamate. To understand better the function of the BF, the organization of the multiple ascending and descending projections of BF neurons is reviewed along with their neurochemical heterogeneity, and possible functions of individual pathways are discussed. It is proposed that BF neurons belong to multiple systems with distinct cognitive, motivational, emotional, motor, and regulatory functions, and that through these pathways, the BF plays a role in controlling both cognitive and non-cognitive aspects of vigilance.
Topics: Animals; Arousal; Basal Ganglia; Humans; Neural Pathways; Prosencephalon
PubMed: 11000416
DOI: 10.1016/s0166-4328(00)00254-0 -
Annals of the New York Academy of... Jun 2004Although initiation of drug abuse occurs primarily during adolescence, little is known about the central effects of nicotine and other abused drugs during this... (Review)
Review
Although initiation of drug abuse occurs primarily during adolescence, little is known about the central effects of nicotine and other abused drugs during this developmental period. Here evidence, derived from studies in rodents, is presented that suggests that tobacco use initiation during early adolescence results from a higher reward value of nicotine. The developmental profiles of the rewarding effects of other abused drugs, such as cocaine, differ from that of nicotine. Using in situ hybridization to quantify mRNA levels of the immediate early gene, cfos, the neuronal activating effects of nicotine in limbic and sensory cortices at different developmental stages are evaluated. Significant age changes in basal levels of cfos mRNA expression in cortical regions are observed, with a peak of responding of limbic cortices during early adolescence. A changing pattern of nicotine-induced neuronal activation is seen across the developmental spectrum, with unique differences in both limbic and sensory cortex responding during adolescence. An attentional set-shifting task was also used to evaluate whether the observed differences during adolescence reflect early functional immaturity of prefrontal cortices that regulate motivated behavior and psychostimulant responding. The finding of significantly better responding during adolescence suggests apparent functional maturity of prefrontal circuits and greater cognitive flexibility at younger ages. These findings in rodent models suggest that adolescence is a period of altered sensitivity to environmental stimuli, including abused drugs. Further efforts are required to overcome technical challenges in order to evaluate drug effects systematically in this age group.
Topics: Adolescent; Animals; Behavior, Animal; Conditioning, Operant; Discrimination Learning; Humans; Models, Animal; Nicotine; Nicotinic Agonists; Prosencephalon; Reward; Self Administration
PubMed: 15251884
DOI: 10.1196/annals.1308.018 -
Journal of Neurobiology Nov 1997This article reviews the organization of the forebrain nuclei of the avian song system. Particular emphasis is placed on recent physiologic recordings from awake... (Review)
Review
This article reviews the organization of the forebrain nuclei of the avian song system. Particular emphasis is placed on recent physiologic recordings from awake behaving adult birds while they sing, call, and listen to broadcasts of acoustic stimuli. The neurons in the descending motor pathway (HVc and RA) are organized in a hierarchical arrangement of temporal units of song production, with HVc neurons representing syllables and RA neurons representing notes. The nuclei Uva and NIf, which are afferent to HVc, may help organize syllables into larger units of vocalization. HVc and RA are also active during production of all calls. The patterns of activity associated with calls differ between learned calls and those that are innately specified, and give insight into the interactions between the forebrain and midbrain during calling, as well as into the evolutionary origins of the song system. Neurons in Area X, the first part of the anterior forebrain pathway leading from HVc to RA, are also active during singing. Many HVc neurons are also auditory, exhibiting selectivity for learned acoustic parameters of the individual bird's own song (BOS). Similar auditory responses are also observed in RA and Area X in anesthetized birds. In contrast to HVc, however, auditory responses in RA are very weak or absent in awake birds under our experimental paradigm, but are uncovered when birds are anesthetized. Thus, the roles of both pathways beyond HVc in adult birds is under review. In particular, theories hypothesizing a role for the descending motor pathway (RA and below) in adult song perception do not appear to obtain. The data also suggest that the anterior forebrain pathway has a greater motor role than previously considered. We suggest that a major role of the anterior forebrain pathway is to resolve the timing mismatch between motor program readout and sensory feedback, thereby facilitating motor programming during birdsong learning. Pathways afferent to HVc may participate more in sensory acquisition and sensorimotor learning during song development than is commonly assumed.
Topics: Animals; Auditory Perception; Birds; Neural Pathways; Prosencephalon; Vocalization, Animal
PubMed: 9369466
DOI: 10.1002/(sici)1097-4695(19971105)33:5<671::aid-neu12>3.0.co;2-c -
Behavioural Brain Research Aug 2018The dorsal diencephalic conduction system (DDC) is a highly conserved pathway in vertebrates that provides a route for the neural information to flow from forebrain to... (Review)
Review
The dorsal diencephalic conduction system (DDC) is a highly conserved pathway in vertebrates that provides a route for the neural information to flow from forebrain to midbrain structures. It contains the bilaterally paired habenular nuclei along with two fiber tracts, the stria medullaris and the fasciculus retroflexus. The habenula is the principal player in mediating the dialogue between forebrain and midbrain regions, and functional abnormalities in this structure have often been attributed to pathologies like mood disorders and substance use disorder. Following Matsumoto and Hikosaka seminal work on the lateral habenula as a source of negative reward signals, the last decade has witnessed a great surge of interest in the role of the DDC in reward-related processes. However, despite significant progress in research, much work remains to unfold the behavioral functions of this intriguing, yet complex, pathway. This review describes the current state of knowledge on the DDC with respect to its anatomy, connectivity, and functions in reward and aversion processes.
Topics: Animals; Diencephalon; Habenula; Mesencephalon; Neural Pathways; Prosencephalon; Reward
PubMed: 29684476
DOI: 10.1016/j.bbr.2018.04.018 -
Current Opinion in Neurobiology Dec 2002One of the challenges when considering the motor control of birdsong is to understand how such a wide variety of temporally and spectrally diverse vocalizations are... (Review)
Review
One of the challenges when considering the motor control of birdsong is to understand how such a wide variety of temporally and spectrally diverse vocalizations are learned and produced. A better understanding of central neural processing, together with direct endoscopic observations and physiological studies of peripheral motor function during singing, has resulted in the formation of new theoretical models of song production. Recent work suggests that it may be more profitable to focus on the temporal relationship between control parameters than to attempt to directly correlate neural processing with details of the acoustic output.
Topics: Animals; Learning; Models, Neurological; Nerve Net; Phonation; Prosencephalon; Respiration; Songbirds; Vocalization, Animal
PubMed: 12490259
DOI: 10.1016/s0959-4388(02)00386-0 -
Trends in Neurosciences Nov 1993The molecular mechanisms that control regional specification, morphogenesis and differentiation of the embryonic forebrain are not known, although recently several... (Review)
Review
The molecular mechanisms that control regional specification, morphogenesis and differentiation of the embryonic forebrain are not known, although recently several laboratories have isolated homeobox, Wnt and other genes that are candidates for playing roles in these processes. Most of these genes exhibit temporally and spatially restricted patterns of expression within the forebrain. However, analysis of the spatial patterns has been complicated because an understanding of the organization of the embryonic forebrain has been lacking. This article describes a neuromeric model of the forebrain that is consistent with the expression patterns of these genes, and that provides a framework for understanding the morphological relationships within this complex structure.
Topics: Animals; Gene Expression; Genes, Homeobox; Genes, Regulator; Mice; Prosencephalon
PubMed: 7507621
DOI: 10.1016/0166-2236(93)90080-6